Background: The category “men who have sex with men” is
used in epidemiology to group same sex behaviors that may result in HIV
transmission. Yet, this category may
obscure important differences among MSM of different sexual identities. We
explored how co-infections with STIs, including HIV, varied by sexual identity among MSM.Methods: Respondent driven sampling (RDS) was used for the first time in Argentina to
recruit MSM. All participants had to be men, 18 years
of age or older, residents of Buenos Aires, who reported having had sex with men at least 10 times in
their lives and at least once in the past six months. Specimens were collected
for HIV and STI detection.Results: A total of 496 MSM were recruited showing a prevalence of 15.7, 22.9,
7.6, 20.2, 2.5 and 82.9 for HIV, HBV, HCV, T.
pallidum (syphilis), Chlamydia and HPV, respectively. (Chlamydia and HPV tests were only performed for
88 and 109 participants.) Men were
divided in four groups based on their reported sexual identity: Gay (25%),
bisexual (36%), heterosexual (22%), other (17%). We analyzed co-morbidity for those STIs for
which we had information for the whole sample (HIV, HBV, HCV, T. pallidum - syphilis).

[Number of STIs by sexual orientation]

Conclusions: MSM identified as gay constituted the biggest
proportion among those affected with one, two, and three different STIs. Prevention efforts focusing on gay identified
men within the MSM group are required.
Focusing prevention efforts on MSM as an encompassing category may miss
important differences observed according to sexual orientation.